56. Classical swine fever (diagnosis, differential diagnosis, prevention, control).

Question 1

Diagnosis?

Answer 1

Diagnosis

• not compulsory to do the test on living animals anymore
• Signs & pathology lesions ʹ suspicion
• Communicable diseaseÆ obligatory lab diagnosis
• Lab tests
• Antigen capture ELISA
• Real-time RT-PCR (ASF is DNA virus so no RT-PCR)
• Virus isolation from the positive cases
• Nucleotide sequencing from the positive cases
• Direct immunofluorescence after frozen sectioning
• Serology
• Indirect, blocking ELISA
• Virus neutralisation test (NPLA)
• Cross-reactions with BVD, border disease virus
• use of monoclonal Abs

Question 2

DD?

Answer 2

Differential diagnosis

• From every febrile, haemorrhagic illness
• ASF ʹ lab diagnosis (wild boar infected with CSF higher than ASF infection)
• Erysipelas ʹ age, season, enlarged spleen
• Salmonellosis ʹ age, no skin haemorrhage, enlarged spleen
• A. pleuropneumoniae ʹ high fever, dyspnoea, rapid death (no haemorrhages)
• Aujeszkys diseaseʹ no skin haemorrhage, age
• Eperythrozoon suis ʹ age, enlarged spleen, icterus
• Porcine circovirus 2 ʹ age, course
• Poisoning ʹ no fever, haematomas
• may be complications of CSF too!

Question 3

Epizootiology?

Answer 3

Epizootiology

• Transmission
• Live, infected swine, transportation, trade
• Raw pork meat,rawpork products(also frozen)
• slaughterhouse,home slaughtering,
• trade, tourism
• Raw pork wastages slaughterhouse, home-slaughtering,restaurants,tourism
• Fomites transportation, trade, tourism
• Humans technician, vet, butcher, salesman
• Wild boar! ʹ no domestic pig cases in the last 5 years
• Very contagious
• Quick spread in the herd
• Virus shedding in the discharges w/in 24h after infection
• Introduction with infected animal: large scale disease in the second week
• Introduction with feed: large scale disease earlier
• Now a days even virulent strains rarely cause high mortality
• Low virulence & vaccine strains
• Subclinical circulation in adult swine or mild clinicalsigns
• Foetal damages
• Immunotolerant piglets
• Long-term carrier & shedder animals
• Seropositive animals in the population (even if no clinical symptoms)
• Vaccinated herd
• Subclinical circulation of the wild type virus too
• Piglets show signs after clearance of maternal Abs (6-12 weeks of age)

Question 4

Prevention, control?

Answer 4

Prevention, control

• In CSF-free countries: avoiding introduction
• Importation restrictions on swine & raw pork meat from endemic countries
• Decontamination of food-remains (restaurants, tourism!)
• Home-slaughters, frozen pork storage!
• Control ʹ contingency plants (restriction zones, slaughtering affected animals, disinfections,
• epizootiology investigations)
• Emergency vaccination in the restriction zone ʹ with EU approval: marking,
• quarantine, separate slaughtering, heat-treated pork, marketing restrictions
• Control of swine transportations & trade
• Closed farms (wild boar)

Question 5

Vaccination?

Answer 5

• Vaccination (Most Countries don’t vaccinate eradicate instead)
• Simultaneous vaccination since the 1940s
• C strain
• Taiwan 800 rabbit passages: attenuated virus(Suvac)
• Produced in rabbits & in cell cultures
• Harmless (even in sow, piglets), no shedding, a few days persistence
• 1x vaccination: 86-94% protection (over 3 months of age)
• Maternal Ab protection until 6-12 weeks of age
• Great help for the eradication
• In CSF-free countries preventative immunisations are forbidden
• Possibility for circulation of the wild-type virus
• Seropositive herd ʹ serological monitoring is complicated
• Possible transplacental infection of vaccinated sows ʹ reproduction problems or
• infected piglets born
• Newer vaccines ʹ subunit, vector, marker vaccines

Question 6

Actual situation?

Answer 6

Actual situation

• CSF is endemic in several European countries (only in wild boar population)
• Within the last few years, wild boars played the main role in the maintenance of CSF in enzootic areas
• In Hungary ʹ wild boar CSF was reported in 2007 in 2 N. Eastern countries
• 51 reported cases in 2007, 164 in 2008, 27 in 2009, 0 reported cases since 2010
• The detected viruses ʹ the one exception ʹ belong to the 2.3 group of CSF: newer European, virulent strain

Question 7

CSF in wild boar?

Answer 7

CSF in wild boar

• Main differences from the domestic swine CSF
• Clinical signs are rarely seen ʹ disturbed behaviour in 4 cases, 5 animals found dead
• Mild pathology lesions
• Only in 10% of the virus positive animals
• Petechial haemorrhages in the dark kidneys
• Petechial haemorrhages in the urinary bladder & colon mucosa
• Mild histopathology lesions ʹ no multiple layer perivascular cuffing in the CNS
• In wild boar petechial haemorrhages are frequent on the kidneys, because of S. choleraesuis.
• Bacterial infarcts are also seen in the kidney

Question 8

Prevention?

Answer 8

Prevention

• Experimental, oral vaccination (buried at least 30cm deep) of wild boars in Germany &
• Slovakia
• Variable success
• Eu supports
• Certain disadvantages
• Labour intensive (individually buried vaccines)
• Not marker vaccine
• Consequent, long term application is necessary
• Limited in Slovakia
• Export considerations
• Control measures (Hungary 2007-2013)
• Enzootic zone for wild boar CSF in the northern countries
• Contingency plants, hunting